What is a key indicator of an infection in a patient?

An elevated white blood cell count is a key indicator of infection because it reflects the body's immune response to pathogens such as bacteria, viruses, and fungi. When an infection occurs, the body produces more white blood cells to fight off the invading organisms. A significantly elevated count can indicate that the body is actively responding to an infection, as the bone marrow releases more white blood cells into the bloodstream. This response is particularly noted with neutrophils, which are usually elevated during bacterial infections.

Other options, while they may indicate various health issues, are not specific indicators of infection. For instance, elevated blood pressure can result from multiple factors including stress, pain, or other medical conditions, but does not specifically signal an infection. Altered mental status might be a consequence of various issues, such as metabolic imbalances, neurological conditions, or severe infections, but it doesn’t directly indicate the presence of an infection. Similarly, a persistent cough may be symptomatic of respiratory infections but is not a definitive or standalone indicator of infection since it can also be caused by allergies, irritants, or other non-infectious conditions.